Hydraulic jump captured air bubble vessel

ABSTRACT

A water-borne air cushion vessel has an underwater driving means on its forward end which creates a hydraulic wave at a distance rearwardly therefrom. The wave produced provides at its crest a constant seal for the forward side of a cavity under the vessel wherein air is trapped to produce the cushioning effect that maintains the vessel above the nominal water level.

[54] HYDRAULIC JUMP CAPTURED AIR BUBBLE VESSEL Edward A. Boydston, 546 AFlordia Street, Vallejo, Calif. 94590 [72] inventor:

[451 May 23, 1972 2,993,462 7/1961 Gough 3,342,032 9/1967 Coxetal..114/67A [22] Filed: Oct. 28, 1970 p Prima Examiner-Andrew H. Farrell21 A l. N ,601 W 1 pp 0 84 Attorney-Owen, Wickersham & Erickson RelatedU.S. Application Data ABSTRACT [63] Continuation-in-part of Scr. No.870,301, Dec. 22,

1969 abandoned A water-borne aucushlon vessel has an underwater drivingmeans on its forward end which creates a hydraulic wave at a distancerearwardly therefrom. The wave produced provides g l l l at its crest aconstant seal for the forward side of a cavity [58] Fi d A 66 5 H underthe vessel wherein air is trapped to produce the e o Searc cushioningeffect that maintains the vessel above the nominal water level.

5 Claims, 6 Drawing Figures 44 r 45 l l l 38 PATENTEDMAY 22 um SHEEI 1BF 2 FIG 1 (PRIOR ART) INVENTOR. EDWARD A. BOYDSTON BY Ohm mm 0ATTORNEYS HYDRAULIC JUMP CAPTURED AIR BUBBLE VESSEL This application isa continuation-in-part of my application Ser. No. 870,301 filed Dec.22nd, 1969 and now abandoned.

This invention relates to captured air bubble vessels or water vehiclesalso referred to as surface effect ships or air cushion vessels.

Such water vehicles or vessels operate on the principle of creating abody of air having an increased pressure underneath it which willsupport or cushion the main hull and superstructure of the vessel justabove the water surface thereby vastly reducing or eliminating waterfriction and hull drag. One problem which arose with such vehicles wasin maintaining the body of air beneath it so as to achieve and retainthe necessary increased air pressure. Various forms of curtain or skinstructures can be made to hold air in along the sides, but it was muchmore difficult to provide a barrier or sea] for the trapped air cushionalong the front of the vessel. The problem was particularly severe forvessels operating in relatively rough or choppy waters.

One object of my invention is to solve the aforesaid problem and providean air cushion vessel that is more stable and reliable by creating andcontrolling a wave that will sealthe front of the vehicle so that theair body or bubble beneathit can be captured. This allows the air to betrapped beneath the vessel and build up to a pressure level higher thanambient air pressure, thereby maintaining the force necessary to raisethe vehicle or vessel up and keep it above the water level.

Another object of my invention is to provide an air cushion type watervessel that can operate with smoothness even in rough water by creatingits own hydraulic jump" wave using a forwardly located propulsion unit.The propulsion unit which may be propellers or underwater jets may beregulated to create a wave with a predetermined amount of energy and ata location that will provide the optimum of sealing effectiveness forall water surface conditions, while also propelling the vessel throughthe water.

Other objects and advantages of my invention will become apparent fromthe following detailed description presented with the accompanyingdrawings, in which:

FIG. 1 is a view in perspective showing a typical air cushion vessel ofthe prior art;

FIG. 2 is a view in perspective showing a vessel embodying theprinciples of the present invention;

FIG. 3 is a view in side elevation of the vessel in FIG 2;

FIG. 4 is a view in perspective of the vessel of FIGS. 2 and 3 takenfrom its underside with portions broken away;

FIG. 5 is a fragmentary view in perspective showing a modified form ofmy vessel utilizing underwater jets for thrust means; and

FIG. 6 is a diagram illustrating the principles of the hydraulic jump asutilized in my invention.

With reference tothe drawing, FIG. 1 illustrates schematically acaptured air bubble vessel 10 of a type currently in limited use.Generally, this vessel has a channel-shaped hull 12 with rigid sidewalls 14 connected to a flexible skirt-like wall [6 at its how and asimilar flexible stern wall skirt that together form a cavity for theair bubble that cushions the vehicle on the waters surface. Drivingpower, indicated by the propellers I8 is at the stern. Vessels of thistype have proven to be successful in limited applications such as onlakes and inland waters where the normal waves are usually very small.However, in even a moderate sea, the captured air bubble vessel of FIG.1, becomes quite impractical due to normal wave action which buffets andbatters the front wall 16. When subjected to the full variance of waveheights and troughs this front wall in rough sea conditions is renderedimpractical and inefficient because the skirt not only is constantlybattered, which slows the forward speed of the vessel, but air from thebubble cavity beneath the vessel can escape under its lower edge. Thiscauses the loss of air cushion pressure and the main hull of the vesselthus lowers and contacts the water.

FIGS. 2-4 show a vessel embodying the principles of my invention whichproduces a hydraulic jump wave to form a front air seal" so that thevessel can operate free of ocean wave variances, and will not bebufieted and battered by large ocean waves. As shown, my vesselcomprises generally a hull 22 with a main deck 24 that can support asuitable cabin or superstructure 26. Extending downwardly from the maindeck are opposite sidewalls 28 that connect with a rear or stem wallflexible skirt 30 to form a central cavity 32 below the main deck. Oneor more fans 34 are positioned within the hull and driven by a suitablepower plant to direct air downwardly within the cavity as inconventional air cushion vehicles. At the forward end of the cavity is ahull portion forming a curved bow 36 that extends between the sidewallsand has a flat underside that curves upwardly at both ends when viewedin a longitudinal vertical cross section. The sidewalls 28 extendforwardly from the bow 36 of the hull and they also taper downwardly inheight toward their forward ends to form relatively narrow portions 38.These narrow portions are connected along their lower edges by atransverse portion 40 to form an open channel which is normallypositioned well below the level of the bow portion 36 and below thenominal water level when the vessel is in normal operation. Mountedbetween the port and starboard forward end portions 38 is a thrustproducing power means. In the embodiment of FIGS. 24, this power meanscomprises a series of motor driven propellers 42 that provide theforward thrust for the vehicle and also produce the hydraulic jump orwave (designated by the dotted line A in FIG. 3) that functions to sealthe air cushion cavity. Any suitable power system, located within thehull-or motors directly adjacent to the propellers can be used to drivethem. In the arrangement shown, the propellers are preferably relativelysmall compared with the width of the channel and are spaced apart in aline extending between the narrow sidewall portions 38 forming the openchannel. As a general rule, as established from actual tests, themaximum height of the hydraulic jump wave that can be produced isroughly five times the diameterof the propeller. On relatively largecraft, a series of three to five propellers may be required to produce asealing wave of adequate height across the full channel distance betweenthe sidewalls 28. Immediately behind the propellers, the open channelextends rearwardly to the open cavity 32 underneath the main deck of thevessel 20 which commences just below the bow portion 36. At the curvedunderside on the forward end of the bow portion are attached one or moreflexible skirt members 44 and similar skirt members 45 are attached onthe trailing curved underside of the bow portion. These skirt membersalso help to maintain the air cushion under the hull at slower speedswhen the jump wave must be lower.

When the vessel 20 is underway with the forward propellers turning, theynot only provide the forward thrust for the vehicle but they alsoproduce a hydraulic jump wave rearwardly that crests just under the bowportion 36. I

As shown-in FIG. 5, the thrust producing power means may comprise one ormore underwater jet nozzles 46 instead of the propellers 42. Here, thenozzles are connected by conduits 48 to a pump 50 mounted on or withinthe vessel hull, which is driven by a suitable power means 52. Suctionconduits which supply water to the pump may be supported by thesidewalls 28.

The principle of the hydraulic jump is well known in the field of fluiddynamics. For example, a full explanation may be found in the textbook,Elementary Fluid Mechanics" by John K. Vennard, published by John Wiley& Sons, Inc.

cal dimensions and specifications for the thrust power propellers 42 orthe nozzles 46 and their location with respect to the curved bow portion36 of the vessel and the flexible curtain or skirt 44 can be ascertainedso that when the thrust producers are operating at their normal rate,the crest of the hydraulic jump wave will occur at just the rightlocation, that is, right at the front curtain.

In operating my vehicle 20, the fan 34 or other means for producing andmaintaining air bubble pressure is first energized. This commences thebuildup of air pressure in the cavity or channel area 32 beneath themain deck of the vessel 26, the air therein being initially confined bythe sidewalls 28, the stern wall curtain 30 and the flexible forwardskirt members 44 and 45. Now, the forward thrust means such as thepropellers 42 are turned on to move the vessel forwardly through thewaters. As these propellers are brought up to speed, the hydraulic jumpwave A is created just under the forward bow portion 36 and the skirtmembers 44. Even though the vessel may move into waters with larger orchoppier waves, the hydraulic jump wave remains at its normal locationat the bow portion of the vessel, providing a constant seal thatprevents the escape of air from the cushioning bubble. Another advantageof the hydraulic jump wave is that its flow aft into the air bubblecavity tends to fill in or replace water that is displaced downward bythe air bubble pressure on the surface of the water traveled over. Thisincreases the efficiency and effectiveness of the air bubble pressuremaintaining force which in turn makes the bubble more secure andreliable, with less tendency for air to leak out from under the vessel.As a consequence, my vessel which can be made in any size, can operatesmoothly in almost any water despite the size of the surface waves. Asillustrated in FIG. 3, the vessel, if made to proper size, will alwaysproduce a hydraulic jump wave that will be larger than surface wavesencountered and thus will always be unaffected by such waves.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. A water borne vessel of the type which is supported at least in partby a body of air, comprising a hull having a main deck with spaced apartsidewall members that extend below the water level and form a cavityunder the main deck for retaining a supporting body of air with aforward opening between the side members;

means for supplying air to said cavity at a pressure which is higherthan ambient air pressure;

means extending forwardly from said hull and forming a channel shapedinlet to said cavity;

and thrust means supported within said inlet for producing an underwaterforward thrust to said vessel and simultaneously a hydraulic jump wavewhich will crest against the underside of said main deck of said hull soas to close said forward opening and prevent air from escaping from saidcavity while the vessel is traveling through the water.

2. A water borne vessel which is described in claim 1 wherein said meansextending forwardly are extended portions of said sidewall members whichtaper to a smaller height and are connected by a transverse portion toform an open channel, said thrust means being supported within saidchannel.

3. A water borne vessel which is described in claim 2 wherein saidthrust means comprises a plurality of relatively small propellersarranged in a line extending transversely across said channel.

4. A water borne vessel which is described in claim 2 wherein saidthrust means comprises one or more jet nozzles for expelling water belowthe nominal water level, and pump means for supplying a constant flow ofwater to said nozzles.

5. A water borne vessel which is described in claim 2 including flexiblecurtain means extending across said channel opening between saidsidewall members.

1. A water borne vessel of the type which is supported at least in partby a body of air, comprising: a hull having a main deck with spacedapart sidewall members that extend below the water level and form acavity under the main deck for retaining a supporting body of air with aforward opening between the side members; means for supplying air tosaid cavity at a pressure which is higher than ambieNt air pressure;means extending forwardly from said hull and forming a channel shapedinlet to said cavity; and thrust means supported within said inlet forproducing an underwater forward thrust to said vessel and simultaneouslya hydraulic jump wave which will crest against the underside of saidmain deck of said hull so as to close said forward opening and preventair from escaping from said cavity while the vessel is traveling throughthe water.
 2. A water borne vessel which is described in claim 1 whereinsaid means extending forwardly are extended portions of said sidewallmembers which taper to a smaller height and are connected by atransverse portion to form an open channel, said thrust means beingsupported within said channel.
 3. A water borne vessel which isdescribed in claim 2 wherein said thrust means comprises a plurality ofrelatively small propellers arranged in a line extending transverselyacross said channel.
 4. A water borne vessel which is described in claim2 wherein said thrust means comprises one or more jet nozzles forexpelling water below the nominal water level, and pump means forsupplying a constant flow of water to said nozzles.
 5. A water bornevessel which is described in claim 2 including flexible curtain meansextending across said channel opening between said sidewall members.